Peter Langman shows few signs of the illness that will one day disable him. But the disease has already changed his life

About me. I'm a 40-year-old, physically fit man, the holder of a PhD in something suitably arcane, with my own house, teeth and hair. But when people ask me how I am, the "Are you well?" of pre-meteorological conversation, my impulse is to reply: "Bar the incurable, degenerative neurological condition, splendid."

About me. I'm a 40-year-old, physically fit man, the holder of a PhD in something suitably arcane, with my own house, teeth and hair. But when people ask me how I am, the "Are you well?" of pre-meteorological conversation, my impulse is to reply: "Bar the incurable, degenerative neurological condition, splendid."

My New Year was somewhat blighted by the revelation that I had acquired Parkinson's disease. That's how I put it. Acquired. Like experience. It just creeps up on you.

But here's the rub: I don't look ill, I don't act ill, I don't even feel ill, yet I am. And this is what's strange. My life hasn't been ruined by this disease — I'm not about to die — but it certainly has changed. The problem is that I don't know what's going to happen: all I know is that something will.

I suppose I knew things were changing three years ago. My legs tired quickly at the gym, ached more. My left arm seemed to be slowing down, so I got hit more often when sparring in karate. I felt it in my fingers, too. Before I traded in rock'*'roll for academia, I was a fire-breathing guitar demi-god. Ok, so I'd hardly touched a guitar in seven years, but now when I picked one up, predictable rustiness became cack-handedness. The coordination was simply gone, and my left hand sometimes refused, like a horse. As for holding a fork, or getting keys out of my pocket? I cover my inability well.

My left-hand stiffness was the excuse I gave for not playing the guitar any more. I demonstrated by holding up my two hands and wiggling the fingers — the left-hand bunch moved in slo-mo. As I performed my finger ballet at a party last summer, my uncle, a professor of medicine, told me I ought to see a neurologist — and later rang my mother to make sure. Finally, after some red-herring investigative physiotherapy, I did.

I was subjected to a battery of joint-wiggling tests, I walked along corridors, scrawled my execrable scrawl, and after half an hour I definitely had Parkinsonism; that is, the symptoms of Parkinson's. Oh, I see, I thought. Hadn't seen that one coming. But I'd need to leak an armful of blood and have an MRI scan to make sure it wasn't something altogether more rare. Well, I lost some blood, got on the train, got off, and lectured on Spenser's Faerie Queene. 'Allegory and darke conceit', it was called. I couldn't have put it better myself.

The waiting for the MRI scan was strange, though I was comfortable that the diagnosis was correct. But I hardly told a soul, just in case it was something else. Then the scan date arrived. This is what happens: you lie on your back and you slide into a tunnel, while your head is semi-clamped into a modern version of a scold's bridle. It has an angled mirror above the eyes so that you can see your shoeless feet and the radiographer in his room as you are subjected to 12 minutes or so of what sounds like a series of ultra-loud dance tracks mixed by two six-year-olds with attention deficit disorder. Then you wait. An hour or three later, a new neurologist repeats the battery of tests, plus air piano. Oh, the scan was fine, she says — no lesions, missing bits or suchlike. I know what that means: the other possibilities have been eliminated. She starts to talk of what happens next and I realise that the words 'you have Parkinson's' haven't actually been said. I ask. She's embarrassed, but confirms. I don't feel anything. After all, I pretty much knew already.

That evening, Newsnight carried a report on the side-effects of the drug for which I clutched a prescription. Now, what do I tell people? Reactions range from scarcely disguised horror to, 'Oh ... what does that mean?' Which is a good question. My Parkinson's may be 'early onset', but it is certainly mild.

No real tremor or involuntary movements (unless I yawn, when my left arm flaps like a stranded pigeon's), some stiffness and general motor inconvenience.

There are 6,000 sufferers of early-onset Parkinson's in the country, many, if not most, of whom will suffer far more than I do. But this is what's so odd. The diagnosis has simply changed my future: it's changed the 'me' I am. Informing the DVLA made me feel a bit, well, 'disabled'. Their list of 'do you haves' was shocking: tremor, involuntary movement, muscle stiffness, narcolepsy, confusion, slowed reactions, depression, shuffling ... the list goes on. Something's inevitable.

And what about my family? If my wife were to become pregnant, what would that mean now? It's a little strange to think that in 10 years, 20 years, five years, whenever, I may need my wife, my child, to care for me. I won't be allowed to drive. I may not be able to work. The fact is, I have no idea what's going to happen. The prognosis is uncertain, except that it will get worse, drugs will become less useful — and don't talk to me about genetically adjusted mice and stem cells. Too late. Already, I rarely sleep beyond 5am. My memory and concentration may deteriorate: great news for an academic. My motor functions and reaction times will deteriorate: great news for someone who hankers after his black belt. And wants to do normal stuff, too. Gradually, I'll be giving it all up in frustration. And frustration with one's own body is not good. I check progress by playing air piano. I was doing it while waiting for the Eurostar the other day. A fellow traveller asks, "Is it a game — do we guess what you're playing?" His wife suggests a Brandenburg concerto. Part of me wants to explain, but it really would embarrass them.

But the fact of diagnosis is that whenever something doesn't quite function, I worry, and lay it at the door of poor old Parky, and while I don't feel exactly old, something has changed. It may seem as if I'm treating this all very lightly, but it's not that — it's simply that there's been no 'oh my god' moment, though perhaps that will come with time.

My old headmaster suffered from Parkinson's, yet I only discovered this after he'd retired. I met him in the street five years later. He displayed the classic Parkinson's tremor. He remembered me, though I was an unexceptional student, and we shook hands, as you do: I felt warmed.